propofed trigonometrical Operation. 201 
taken for a mean latitude, unlefs there fhould be fufficient 
grounds for rejeding any from the number, as differing too 
much from the others. Hence it is, that philofophers are not 
yet agreed in opinion with regard to the figure of the earth ; 
fome contending, that it has no regular figure, that is to fay, 
not luch as. would be generated by the revolution of a curve 
around its axis. Others have fuppofed it to be an ellipfoid ; 
regular, if both polar Tides fhould have the fame degree of 
flatnefs ; but irregular, if bne fhould be flatter than the other. 
And, laftiy, fome fuppofe it to be a fpheroid differing from the 
ellipfoid, but fuch as would be formed, neverthelefs, by the 
revolution of a curve around its axis; although in this cafe 
too one polar fide may not be fimilar to, but more or lefs oblate 
than the other. 
In order, therefore, to put this matter in its true light, and 
to enable every one to judge, by limple infpeCtion only, which 
of the theories agrees bcft with actual meafurement, I have 
computed on ten different hypothecs , and arranged in their 
order, the lengths of the arc between Greenwich and Perpig- 
nan ; as alfo fome other chief properties of each figure, which 
laft fill up the fpace towards the bottom of the table. This 
mode of collecting the refults feemed to me to be the mofl 
di/tindt that could be followed, to avoid that perplexity which 
muft for ever occur in referring back to, and comparing, many 
numbers together, computed on different fyftems, when the 
whole are not placed before the eye at once. 
The firft of the eleven columns, or that which comes next 
to the celeftial arc, contains the mealured portions of the cor- 
refponding terreftrial arc, as far as they have yet been exe- 
cuted. The blanks at top cannot he fupplied, until we fhall 
Vol. LXXVII. D d have 
